The present invention relates generally to a system and method for determining the hydrocarbon emission from point sources located within an automotive vehicle.
It is known to those skilled in the art that an automotive vehicle at rest releases hydrocarbons to the atmosphere which may be fuel, lubricant, or polymer based, the latter emanating from plastic components. The mass of hydrocarbons emanating from a vehicle at rest is typically determined by placing the vehicle in a test facility and performing a Sealed Housing for Evaporative Determination (SHED) test procedure, in which gases within the test facility are drawn into a flame ionization detector (FID) periodically over a 72-hour test period. Based on the concentration of hydrocarbons detected by the FID and the SHED volume, the mass of hydrocarbons emitted by the vehicle can be determined.
The inventors of the present invention have recognized a need to measure the mass of hydrocarbons emanating from discrete portions of a vehicle. Stringent emission regulations, which limit hydrocarbon emission, necessitate the capability to precisely measure all hydrocarbon sources. For example, hydrocarbons may be emitted from the vehicle through the vehicle""s air induction system (AIS). Hence, it is desirable to measure the mass of hydrocarbon material emanating from the AIS to substantially ensure that the vehicle is in compliance with these emission regulations, to allow diagnostic tests to be conducted, and to allow various designs to be evaluated.
It has previously been attempted to measure point source or subassembly emissions by forcibly drawing out hydrocarbon material from the subassembly. These have been found to provide a false indication of the amount of hydrocarbons. Furthermore, these prior methods to measure subassembly emission of hydrocarbons: are complex, are costly, and require a relatively extensive amount of modification to the vehicle. Such methods may also interfere with the normal operation of the vehicle, eg., testing other than SHED testing.
The inventors of the present invention have determined a method and apparatus for determining point source hydrocarbon emissions without intrusion upon the normal operation of the vehicle or the results of the SHED test.
Disadvantages of prior art systems are overcome by a system for measuring an amount of material emitted from a portion of a vehicle, which includes: a collection fixture coupled to the portion of the vehicle, a sampling tube fitted to the collection fixture; a pump coupled to the sampling tube for drawing gases near the portion of the vehicle to which the collection fixture is coupled and an analyzer for receiving the gases and for producing a concentration signal proportional to the concentration of the material pumped through the analyzer.
The present invention further provides a method for measuring a flow rate of hydrocarbons emitted from a portion of a vehicle wherein a pump draws gases from the portion of the vehicle. In the method an indication of a flow rate of the gases and an indication of hydrocarbon concentration of the gases are provided. Based on the flow rate and concentration, a flow rate of hydrocarbons emitted from the portion of the vehicle can be determined.
A primary advantage of the present invention is that this method and apparatus permits an accurate determination of the role of a vehicle subassembly or point source in contributing to the overall vehicle hydrocarbon emissions.
A further advantage is that the present invention does not impair the measurement accuracy of the vehicle""s total hydrocarbon emission in the SHED test.
Yet another advantage is that the intrusion upon the vehicle and the modifications required are minimal. For example, to make such a measurement on the AIS, a tube is inserted into an air intake conduit. The tube may be left in place and still allow the vehicle to be normally operated or tested for other purposes.
Another advantage of the present invention is that the point source or subassembly of the vehicle that is being tested need not be removed from the vehicle to determine the hydrocarbon emission from the point source during the SHED test. Furthermore, a special test facility is not required to perform point source or subassembly measurements as the SHED test facility may be used for this purpose. Additionally, the point source hydrocarbons may be measured concurrently with the total vehicle hydrocarbon measurements; thus, efficiently employing a SHED test facility.
A further advantage is that the measuring apparatus is not complicated or expensive.